Data reduction for the MIPS far-infrared arrays

Traditional photoconductive detectors are used at 70 and 160 microns in the Multiband Imaging Photometer for SIRTF. These devices are highly sensitivity to cosmic rays and have complex response characteristics, all of which must be anticipated in the data reduction pipeline. The pipeline is being developed by a team at the SIRTF Science Center, where the detailed design and coding are carried out, and at Steward Observatory, where the high level algorithms are developed and detector tests are conducted to provide data for pipeline experiments. A number of innovations have been introduced. Burger's model is used to extrapolate to asymptotic values for the response of the detectors. This approach permits rapid fitting of the complexities in the detector response. Examples of successful and unsuccessful fits to the laboratory test data are shown

Data reduction for the MIPS far-infrared arrays

Traditional photoconductive detectors are used at 70 and 160 microns in the Multiband Imaging Photometer for SIRTF. These devices are highly sensitivity to cosmic rays and have complex response characteristics, all of which must be anticipated in the data reduction pipeline. The pipeline is being developed by a team at the SIRTF Science Center, where the detailed design and coding are carried out, and at Steward Observatory, where the high level algorithms are developed and detector tests are conducted to provide data for pipeline experiments. A number of innovations have been introduced. Burger's model is used to extrapolate to asymptotic values for the response of the detectors. This approach permits rapid fitting of the complexities in the detector response. Examples of successful and unsuccessful fits to the laboratory test data are shown

Integrable N = 2 Landau-Ginzburg Theories from Quotients of Fusion Rings

The discovery of integrable $N=2$ supersymmetric Landau-Ginzburg theories whose chiral rings are fusion rings suggests a close connection between fusion rings, the related Landau-Ginzburg superpotentials, and $N=2$ quantum integrability. We examine this connection by finding the natural $SO(N)_K$ analogue of the construction that produced the superpotentials with $Sp(N)_K$ and $SU(N)_K$ fusion rings as chiral rings. The chiral rings of the new superpotentials are not directly the fusion rings of any conformal field theory, although they are natural quotients of the tensor subring of the $SO(N)_K$ fusion ring. The new superpotentials yield solvable (twisted $N=2$) topological field theories. We obtain the integer-valued correlation functions as sums of $SO(N)_K$ Verlinde dimensions by expressing the correlators as fusion residues. The $SO(2n+1)_{2k+1}$ and $SO(2k+1)_{2n+1}$ related topological Landau-Ginzburg theories are isomorphic, despite being defined via quite different superpotentials.Comment: 34 pages, BRX-TH-34

Fusion rules in conformal field theory

Several aspects of fusion rings and fusion rule algebras, and of their manifestations in twodimensional (conformal) field theory, are described: diagonalization and the connection with modular invariance; the presentation in terms of quotients of polynomial rings; fusion graphs; various strategies that allow for a partial classification; and the role of the fusion rules in the conformal bootstrap programme.Comment: 68 pages, LaTeX. changed contents of footnote no.

Performance of the multiband imaging photometer for SIRTF

We describe the test approaches and results for the Multiband Imaging Photometer for SIRTF. To verify the performance within a `faster, better, cheaper' budget required innovations in the test plan, such as heavy reliance on measurements with optical photons to determine instrument alignment, and use of an integrating sphere rather than a telescope to feed the completed instrument at its operating temperature. The tests of the completed instrument were conducted in a cryostat of unique design that allowed us to achieve the ultra-low background levels the instrument will encounter in space. We controlled the instrument through simulators of the mission operations control system and the SIRTF spacecraft electronics, and used cabling virtually identical to that which will be used in SIRTF. This realistic environment led to confidence in the ultimate operability of the instrument. The test philosophy allowed complete verification of the instrument performance and showed it to be similar to pre-integration predictions and to meet the instrument requirements

On-orbit performance of the MIPS instrument

The Multiband Imaging Photometer for Spitzer (MIPS) provides long wavelength capability for the mission, in imaging bands at 24, 70, and 160 microns and measurements of spectral energy distributions between 52 and 100 microns at a spectral resolution of about 7%. By using true detector arrays in each band, it provides both critical sampling of the Spitzer point spread function and relatively large imaging fields of view, allowing for substantial advances in sensitivity, angular resolution, and efficiency of areal coverage compared with previous space far-infrared capabilities. The Si:As BIB 24 micron array has excellent photometric properties, and measurements with rms relative errors of 1% or better can be obtained. The two longer wavelength arrays use Ge:Ga detectors with poor photometric stability. However, the use of 1.) a scan mirror to modulate the signals rapidly on these arrays, 2.) a system of on-board stimulators used for a relative calibration approximately every two minutes, and 3.) specialized reduction software result in good photometry with these arrays also, with rms relative errors of less than 10%

Two topics in 2D quantum field theory

Two topics in two-dimensional quantum field theory are presented. The first is a classification of 2- and 3-field rational conformal field theories. Using the fact that the fusion algebra of a RCFT is specified in terms of integers that are related to modular transformation properties, we classify 2- and 3-field chiral RCFT's. We show that the only possibilities for the non-trivial fusion rule in the 2-field case are φ x φ = 1 or φ x φ = 1 + φ. Similar results are obtained for the 3-field case. A partial classification of possible conformal dimensions and central charges for these theories is also obtained. The second topic is in two-dimensional quantum gravity. Explicit computation of the non-perturbative correlation functions of the (1, q) models of KdV-gravity is presented. This computation includes contributions from high genus as well as correlation functions of descendant fields. A ghost number conservation law for these models is derived from purely algebraic considerations. A hint of further selection rules is found